A turret is one of two knobs in the outside center part of a riflescope body. Turrets are marked in increments and are used to adjust elevation and windage for points of impact change. Conventional turrets have markings on them that indicate how many clicks of adjustment have been dialed in on the turret, or an angular deviation, or a distance compensation for a given cartridge. A click is one tactile adjustment increment on the windage or elevation turret of a scope.
In order to achieve accurate sighting of objects at greater distances, the downward acceleration on the projectile imparted by gravity is of greater significance. The effect of gravity on a projectile in flight is often referred to as bullet drop because it causes the bullet to drop from the shooter's line of sight. For accuracy at longer distances, the sighting components of a gun must compensate for the effect of bullet drop. An adjustment to the angular position of the rifle scope relative to the rifle barrel is made using the elevation turret to compensate for bullet drop.
A zero point for the scope is determined by adjusting the angular position of the rifle scope relative to the rifle barrel until the impact point of the bullet matches a target at a known distance when viewed through the scope reticle. For targets at greater distances than the distance used for establishing the scope's zero point, the elevation turret is used to adjust the angular position of the scope with respect to the rifle barrel to compensate for the greater amount of bullet drop.
Conventional elevation turrets allow for multiple rotations in order to enable the scope to compensate for longer-range targets. Unfortunately, because conventional turrets lack a zero stop mechanism, the zero point can be easily lost when elevation is dialed. Even when the turret's markings are visible, the user may miss the zero point by one or more rotations if he or she does not carefully count the number of rotations both while dialing away from the zero point and when dialing towards the zero point.
Another difficulty with existing rifle scopes is that certain operating conditions require the user to remember both how many clicks and the direction of rotation needed to return the elevation turret to its zero point from a different setting. When light conditions are poor, such as at twilight, night, or in darkened rooms of buildings, or if it is difficult for the user to hear or feel the clicks, it is very easy for the user to lose track of what adjustment is needed to return to the zero point. Under such conditions, the markings may not be sufficiently visible. This is particularly significant for police and military users of firearms, who in the course of their duties may very likely be confronted with a threat under poor lighting conditions. In addition, hunters may hunt at twilight or in deep shade.
Because of the need for compact riflescope components, markings are necessarily small, making them difficult to read under borderline conditions. While this may be a concern when making fine adjustments, it is of greater concern when a user must make large changes involving several revolutions of a knob, which may lead to an error in the number of revolutions made.
Turrets that prevent downward advancement of the turret screw beyond a preset zero point are known. One such device is shown in U.S. Pat. No. 6,643,970 to Huber, titled “Zero Stop Adjustable Rifle Scope.” This “zero stop” rifle scope adjustment mechanism enables the user to position a stop ring and lock ring on the turret screw to prevent downward advancement of the turret screw beyond a position associated with the scope's zero point. The disclosed device makes it easy for the user to return to the zero point after adjusting the scope for a longer-range target and prevents the user from over adjusting beyond the zero point.
The Huber device suffers the disadvantage of requiring the user to perform a complex series of operations in order to configure the zero stop rifle scope adjustment mechanism. The user is required to hold the turret screw in the desired position associated with the zero point while simultaneously rotating the stop ring downward over the turret screw until it makes contact with the index dial. The user then has to continue to hold the turret screw in the desired position associated with the zero point while rotating the lock ring downward onto the adjustment bolt until the lock ring makes contact with the stop ring. Finally, the user has to continue to hold the turret screw in the desired position associated with the zero point while tightening screws to lock the stop ring and lock ring together and to bind them to the turret screw. Performing all of these operations without inadvertently changing the position of the turret screw and introducing error into the zero stop adjustment mechanism is extremely difficult.
Furthermore, the Huber design uses small aluminum tabs to stop rotation, which result in a very small contact surface area. Each tab has an area less than 1 square mm, and the tabs are only about 1.5 mm thick. Their small size and aluminum composition make Huber's tabs prone to creep and/or shearing with repeated use. The Huber design is therefore vulnerable to having an undesirably short service life.
In addition, the Huber design requires the user to expose the internal clicker mechanism and zero stop mechanism to the elements in order to set the zero stop. In sandy, dusty, and dirty environments, exposure could cause Huber's zero stop or clicker mechanism to become contaminated by foreign material. This could result in reduced performance or even render them inoperable over time.
Finally, the Huber design is known to experience movement of its zero stop when the turret is spun into the stop surface hard enough. Any movement of the zero stop causes the user to have to reset it again, making such movement highly undesirable. Rapid, forceful movements of the turret could readily occur under stressful conditions, such as an enemy closing in on a position in combat, resulting in the zero stop being thrown off at the worst possible time.
Therefore, a need exists for a new and improved rifle scope with adjustment stop that prevents adjustment of a turret beyond a preset amount. In this regard, the various embodiments of the present invention substantially fulfill at least some of these needs. In this respect, the rifle scope with adjustment stop according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of preventing adjustment of a turret beyond a preset amount.